Abstract There are approximately 240,000 U.S. taxi/limousine drivers in the U.S.(1). New York City (NYC) is home to 42,000 taxi drivers, 84% of whom are immigrants (2). NYC taxi drivers work long hours (10-12 h/d shifts, ~6d/wk), often in heavy traffic (2). Exposure to high levels of respirable particulate matter (PM) Is closely linked to increased hospital admissions, lung cancer risk and mortality, and respiratory and cardiopulmonary mortality (3-9). Two studies have demonstrated high lung cancer prevalence among professional drivers, after adjusting for smoking, suggesting an association with PM exposure (10, 11). In a reanalysis of the Harvard Six Cities Study, each 10 upsilon g/m 3 increase in PM2.5 exposure was associated with an adjusted increased risk of all-cause mortality of 14% (95% Cl: 7, 22), and with a 37% (95% Cl: 7, 75) increase in lung cancer mortality (12). A 26- year prospective study found that each 10 upsilon g/m 3 increase in PM2.5 (PM <2.5 pm) exposure is associated with a 15-27% increase in lung cancer mortality among never-smokers (3). Taxi Particulate matter Study (TIPS) Is a community-engaged T1-T4 translational research study for at-risk taxi drivers in NYC. TIPS will address the following key research questions: 1) the extent to which excess PM exposure is associated with adverse changes in physiologic and biochemical markers, by comparing drivers with a driver-nominated non-taxi-driver peer comparison group; 2) the effect of an in-taxi HEPA filtration intervention on decreasing PM exposure and associated biomarker levels among taxi drivers randomized to the HEPA intervention in comparison with taxi drivers randomized to a control group. Participating taxi drivers will be randomized with a 1:1 ratio into either the control condition or the HEPA filter intervention condition. A third, driver-nominated matched peer reference group will serve as non-taxi-driver controls.